Financial Calculator
Solve for any missing loan variable — find your monthly payment, discover how long it takes to pay off a loan, or uncover the implied interest rate — all with a full amortization schedule and real-time charts.
Payment Calculator
Choose what to solve, then fill in the known values
Monthly Payment
$283.23
Monthly Payment
$283.23
Per month
Total Interest
$1,994.00
Cost of borrowing
Total Cost
$16,994.00
Principal + interest
Interest % of Loan
13.29%
Interest ÷ principal
| Year | Principal Paid | Interest Paid | Remaining Balance |
|---|
The Formula
Three different formulas apply depending on which variable you're solving for. All three derive from the standard amortization equation — the same math used by every bank and lender. For interest rate, there's no closed-form solution, so the calculator uses Newton–Raphson iteration.
Formula
About This Tool
A payment calculator tells you the exact monthly cost of any loan before you ever sign — letting you budget accurately, compare lenders, and avoid over-borrowing. Even a 0.25% rate difference on a $200,000 loan saves over $10,000 in interest over the life of the loan.
This tool runs in three modes: solve for the monthly payment, the loan term, or the interest rate. Whichever variable you don't know, the calculator works it out from the others using the standard amortization equation (or Newton–Raphson iteration when solving for rate).
Pair the result with the amortization schedule to see how each payment splits between principal and interest year by year — and where extra principal payments would have the biggest impact on your total interest cost.
Budget Before You Borrow
Know your exact monthly payment before applying so you don't overextend.
Compare Loan Offers
Run rate, term, and down-payment scenarios side-by-side instantly.
Plan Early Payoff
Use Find Term mode to see how a higher payment shortens the loan.
Amortization Insight
Year-by-year split of principal vs interest reveals best prepayment timing.
Find the Hidden Rate
Reverse-solve a quoted payment to find the embedded APR.
Refinance Decisions
Quantify exact savings before commiting to a refinance.
Three modes, four inputs, instant answers — solve any loan variable in seconds.
Pick Monthly Payment, Loan Term, or Interest Rate. The unknown field is hidden automatically.
Type or slide the loan principal — the amount being borrowed before any fees. For refinancing, use your current remaining balance.
Provide the rate & term (to find payment), rate & payment (to find term), or payment & term (to find rate).
The solution appears at the top with stat boxes for monthly payment, total interest, total cost, and interest as % of the loan.
The Over time tab plots principal vs interest each year; the Breakdown donut shows the principal-to-interest ratio.
The Schedule tab shows annual principal/interest paid and remaining balance to plan extra-principal payments.
Everything you need to know about loan payments, amortization, and how this calculator solves for any missing variable.
The formula is M = P × r(1+r)ⁿ / [(1+r)ⁿ − 1], where P is the loan amount, r is the monthly interest rate (annual ÷ 12), and n is the number of payments. This ensures each fixed payment covers accrued interest plus a growing portion of principal.
The algebraic formula is n = −log(1 − P·r/M) / log(1+r). This works only when the monthly payment M is greater than the first month's interest P·r. If your payment is too low, the balance grows and the loan can never be paid off.
Monthly payment is only moderately sensitive to rate changes. A 1% rate reduction on a 30-year mortgage reduces the payment by roughly 6–7%. The bigger impact is on total interest — that same 1% reduction saves you tens of thousands over the loan term.
Extra principal payments directly reduce your outstanding balance, which means less interest accrues in subsequent months. This shortens your loan term and reduces total interest paid — often significantly. Use "Find Term" mode with a higher payment to model the impact.
In the early months of a loan, most of your payment goes toward interest and very little reduces principal. This is because interest is calculated on the full remaining balance. By paying extra early, you reduce that base faster — dramatically cutting the interest that accrues over the remaining term.
A shorter term locks you into a higher required payment but guarantees the savings. Extra payments on a longer-term loan give you flexibility — you can pay more when cash is available and less when it isn't. Many financial advisors recommend the flexibility of a longer term with regular extra payments.
No — this calculator shows the pure principal-and-interest (P&I) payment. For mortgages, your actual payment may also include property tax, homeowner's insurance, and PMI in escrow. Use our Mortgage Calculator for a complete PITI payment estimate.
Most lenders prefer a total debt-to-income (DTI) ratio below 36%, with no more than 28% going toward housing. To calculate your DTI, divide your total monthly debt payments by your gross monthly income.